ALso allow release files with .yml ending
ALso allow release files with .yml ending

I.e. osprofiler ends with .yml [1].

[1] https://github.com/openstack/releases/blob/master/\
    deliverables/newton/osprofiler.yml

Change-Id: I31010633b068441420de2e3bf196dac712a02a2f

openstack/rpm-packaging-tools